Various circuit structures exist that map a monitored voltage to a current magnitude. These circuits often utilize some form of emitter-follower arrangement using bipolar, J-FET or MOSFET devices that exhibit voltage offsets that marginalize the transfer function accuracy. Operational amplifiers (op-amps) are often incorporated into the feedback paths of these devices in an attempt to correct these offset errors and improve precision. However, the use of op-amps reduces operating bandwidth and increases settling times. Moreover, these devices typically require input voltage levels limited to the supply voltage range of the circuit.
These limitations are problematic as many applications (for example, switched mode power conversion) require voltage to current conversion at voltage levels that are orders of magnitude greater than the circuit supply levels. And while voltage dividers may be used to lower input voltage levels between circuit supply levels, such arrangements introduce paths for noise in addition to decreasing the signal bandwidth. Moreover, digital low voltage supplies often require voltage level monitoring at fractions of the bias supply. Further still, in switched mode power converters, voltage to current transduction is required to monitor transient events, thereby requiring both wide bandwidth and fast transient response.
Alternative voltage to current converter arrangements are desired.